Automatic focusing device

ABSTRACT

A camera having an electrical power supply, a light emitting shutter, an objective lens, and apparatus for automatic focusing having first and second lenses. Modulated radiant energy of predetermined frequency is transmitted through the first lens toward the subject. The reflected image from the subject is passed by the second lens and received by a light sensitive transducer. The energy emitting source and the light sensitive transducer are displaced in unison to vary the modulated radiant energy reflected from the subject. Electronic detection circuitry is coupled to the light sensitive transducer to develop an output signal when the modulated radiant energy incident on the light sensitive transducer is at a maximum. The output signal is applied to arrest further displacement of the energy emitting source and the light sensitive transducer. The objective lens is moved toward a position that is determined by the displacement of the energy emitting source and the light sensitive transducer.

United 5 [1113599552 [72] Inventor Donald M. Harvey Priniary Examiner-Samuel S. Matthews Webster, N.Y. Assistant Examiner-E. M. Ber [21] Appl.No. 853,093 AtlorneysRobert W. Hampton and William C. Dixon, Ill [22]Filed Aug. 26, 1969 j [45] Patented Aug. 17, 1971 [73] Assignee EastmanKodak Company ABSTRACT: A camera having an electrical power supply, a

Rochester, NY. light emitting shutter, an objective lens, and apparatusfor au- 3,450,0l8 6/1969 John,Jr.

tomatic focusing having first and second lenses. Modulated m radiantenergyof predetermined frequency is transmitted [54] AUTOMATIC FOCUSINGDEVICE through the first lens toward the subject. The reflected image 8Claims, 7 Drawing Figs from the subject is passed by the second lens andreceived by a light sensitive transducer. The energy emitting source andthe U.S. Cl C, Sensitive transducer are displaced in unison to y the95/45250/2Ol modulated radiant energy reflected from the subject. Elec-[51] Ilfl. Cl G03b 3/00 I m detection circuitry is coupled to the lightsensitive 50 Field of Search 95/44 R, 44 mnsducer to develop an outputSignal when the modulated 45; 250/201 radiant energy incident on thelight sensitive transducer is at a maximum. The output signal is appliedto arrest further dis- [56] References cued placement of the energyemitting source and the light sensitive UNITED STATES PATENTStransducer. The objective lens is moved toward a position that 3,443,5025/1969 Harvey 95/44R is determined by the displacement of the energyemitting 5/45 source and the light sensitive transducer.

BANDPASS TRIGGER r- FILTER C'RCUT CLAMPING MEANS PATENTED AUG] 7 l9?!SHEET 1 IJF 3 74 FIG. 6

DONALD M. HARVEY INVENTOR.

BY M4. 6Y9

ATTORNEYS PATENTEU mm 7:97:

SHEET 2 OF N 6E J 3/ DONALD M. HARVEY INVENTOR.

Sh umh m0 ATTORNEYS AUTOMATIC FOCUSING DEVICE BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to anautomatic focusing and range finder mechanism suitable for use in acamera or the like.

2. Description of the Prior Art It is broadly known in the prior art touse reflected light from a subject for the purpose of determining rangedistance. One of the major difficulties in the art has been toeffectively use the reflected signal so as to precisely determine whentrue focus occurs.

SUMMARY OF THE INVENTION The invention relates to an apparatus fordetermining the range distance to a subject of interest. In onedisclosed embodiment of the invention, energy emitting means areprovided for transmitting modulated radiant energy of predeterminedfrequency through a first lens toward the subject. The reflected imagefrom the subject is received by a second lens and passed to a lightsensitive means. Displacement means are adapted to move the energyemitting means and the light sensitive means in unison to vary themodulated radiant energy reflected from the subject. Means are coupledto the light sensitive means for developing an output signal wen themodulated radiant energy incident on the light sensitive means is at amaximum.

In another embodiment, the first and second lenses are masked so as toexaggerate out of focus conditions to enable easier detection of themaximum modulated radiant energy incident on the light sensitive means.

It is an object of the instant invention to provide an automaticmechanism which will quickly and accurately enable the determination ofdistance without elaborate manual manipulation being required.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a pictorial view of a stillcamera utilizing an automatic focus and range finding mechanism inaccordance with the invention;

FIG. 2 is a schematic diagram showing the automatic focus and rangefinding mechanism in accordance with one illustrative embodiment of theinstant invention;

FIG. 3 is a wave form diagram of photocurrent vs. lens displacement usedin explaining the operation of the embodiment of FIG. 2;

FIG. 4 is a schematic diagram showing a second illustrative embodimentof the instant invention;

FIG. 5 is a wave form diagram of photocun'ent vs. lens displacement usedin explaining the operation of the embodiment of FIG. 4; and

FIGS. 6 and 7 are explanatory schematic diagrams of certain componentsfound in the embodiment of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is hereillustrated in conjunction with a stiti camera, but it should of coursebe understood that the inventive concept is equally useful in anyapparatus where automatic focus and range findings are required to beaccom- One embodiment of the automatic focus and range determiningmechanism of the instant invention is illustrated in FIG. 2. A source ofmodulated radiation is indicated generally at 32, and in this particularembodiment may conveniently comprise an incandescent lamp 3 3 having astraight line filament 36. The radiant energy emitted by the lamp 34 ismodulated in any convenient manner such as by a mechanical chopperindicated at 38 and suitable driven by a prime mover source (not shown)to provide a predetermined modulated frequency. A

A photosensitive transducer means, indicated generally at 40, comprisesa photosensitive cell 42. While the radiation source 32 and thetransducer 40 may be conveniently arranged in a housing 44, they mayalso be independently supported. As will be seen as the descriptionproceeds, the radiation source 32 and the photosensitive transducermeans 40 are moved in unison. An electric motor as is mechanicallycoupled to the housing 44, as indicated symbolically at 47, so as tomove the modulated radiation source 32 and the photosensitive transducermeans 40 in the direction indicated by the arrow at 48. The motor 46 isenergized by power supply 49, when the release member 20 is actuated toclose switch 53, and is arranged to be displaced through a predeterminedrota tional displacement based on the total distance housing 44 is to bemoved, i.e., from the near hyperfocal setting for the objective lens 12of the camera. The motor 46 is biased by s pring means 51 to return toits initial position after the motor shaft is unclamped, as will beexplained when the operation of the FIG. 2 embodiment is discussed ingreater detail. A range determining cam means 50, having a cam surfacewhich is a function of range distance, is coupled, as indicated by thedashed line, for rotational displacement with the motor shaft. Theobjective lens 12 in this embodiment is coupled directly to the cammeans 50 by means (not shown) which include a follower to engage thecontoured surface of cam means 50. As the cam 5b rotates, the objectivelens 32 is successively moved through various focal setting untildisplacement is arrested at true focus for the subject.

The light from the straight line filament 36, after modulation by thechopper 38, is projected toward a subject, indicated here symbolicallyby a planar surface identified at 66, to produce an image at 52 which isreflected to and received by the lens 30 and imaged on the photocellexposed slot surface 42.

The electrical output of the photosensitive transducer means 40 iselectrically coupled to a band pass filter means 54, and thensuccessively passed to an amplifier means 56, a peak detector means 5%,and a trigger circuit means 60. The output signal of the trigger circuit60 is applied to a clamping means 62.

Completing the description of FIG. 2, the shutter release member 22 isadapted to open switch 53, and is coupled to a shutter indicatedsymbolically at S, as will be later explained.

OPERATION OF THE PREFERRED EMBODIMENT In operation of the camera, theoperator observes a subject as through the view finder 18 (FIG. ll), andthe focus determining release member Zll is depressed close switch 53 toenergize the electric motor 46 and the circuitry at 5d, 56, 58, and s2.Switch is arranged to ren'lain closed after release of member 20 and tobe subsequently opened by operation of the shutter release member 22.The rotation of the motor 46 causes the housing 44 to be displaced inthe direction indicated by the arrow d8.

Referring now especially to FIG. 2, when the filament is in true focuson the subject 66, the line filament will be imaged at 52. In any otherposition either side of true focus, the filament imaged on the subject66 will be enlarged as indicated in dotted outline at 63. The enlargedimage will therefore be reflected as an enlarged image on the photocellexposed slot 42 as indicated at 70.

In FIG. 3 there is a curve depicting photocurrent as ordinate and lensdisplacement as abscissa. When the line filament 36 is in true focus onthe subject es, maximum photocurrent will obtain as indicated by theordinate at 64. In any other position a smaller photocurrent willresult. When, for example, the photocell receives the image indicated at70, a smaller photocurrent will be obtained because the photosensitivesurface is receiving lees radiant energy.

The light transmitted from the source of radiation 32 is modulated bythe mechanical chopper 38; the signal reflected to the photocell surface42 is thus also modulated, The band pass filter 54 is arranged to pass aband frequency including the predetermined frequency such as, forexample, 2.5 kilo Hz. The modulated photocurrent from the photosensitivetransducer means 40 is passed to the band pass filter 54, whichattenuates other frequencies outside the band. The filtered output ispassed to amplifier .56 and then to a peak detector 58 which, when themaximum signal is detected, sends an output to the trigger circuit means60 which sends a trigger signal to the clamping means 62, which mayinclude solenoids energized in response to said trigger signal to holdthe motor shaft against further rotation. The range determining cam 50,which is mounted on the motor shaft, then comes to rest, and since theobjective lens 12 is in contiguous contact with the cam 56, the objectlens i2 is now in correct focus with respect to the subject 66.

The objective lens 12. of the camera it) is now in focus, and the camerauser depresses the shutter release member 22, which first permits lightto enter the camera through the objective lens 12 for actual picturetaking, and then opens switch 53; to disconnect the power supply 49 tothereby deenergize the circuitry 54, 56, 58, so, as well as the motor36. Next, the spring means 51 rotates motor 46 to return the housing 44to its initial position.

ESCRIPTION OF AN ALTERNATIVE EMBODIMENT An alternative embodiment of theautomatic focus and range finding mechanism is shown in PEG. 4. As maybe seen from a study of FIG. 3, the peak photocurrent at ordinate 6 hasa modestly rounded configuration, so that detection of the maximum issomewhat difficult as the peaic is approached. It would be helpful insome applications to have a maximum peak that would be much sharper tomake for easier and more accurate detection. The embodiment of FIG. 4 isintended to provide a photocurrent vs. lens displacement curve similarto that depicted in FIG. 5, where, with the same radiation source 32, asomewhat sharper peak obtains, although with some sacrifice in thesignal amplitude. As will be understood presently, it is preferably tosacrifice the diminution in signal magnitude in order to provide foreasier peak detection. (If one desires that there be no loss of signalamplitude, then one need only increase the magnitude of the radiationsource 32.)

Referring now especially to FIG. 4, where the same numeration has beenretained in identifying similar parts, the lends 28 is partially coveredby masking members 72, 7d, and the lens contains a masking element 76positioned on its optical axis.

This arrangement of the lenses 28, 30 may best be appreciated from astudy of FIGS. (6 and i. The use of the masking means 72, 74 (PEG. 6)narrows the width of light beam being sent out from the source ofradiation towards the subject 66. As shown in FIG. I, the reflectedenergy from the subject 66 is then passed through the lens 30, which,because of the mask 76, retracts the received light in a pattern havingthe general configuration of a centrally hollowed cone, as indicated bycross section at 78, 30.

in both the FIG. 2 and FIG. 4 embodiments the lens I2 may be eitherdisplaced concurrently with the cam 50 or the lends may be later movedtoward the stop afforded by the arrested cam 50 prior to the picturetaking.

in the FIG. embodiment, the lens 12 is not displaced concurrently withthe cam 50; instead, objective leans i2 is arranged to be displacedtoward the cam surface of cam 50 upon actuation by the shutter releasemember 22. This may be accomplished in one convenient manner by biasingthe lens 512 in thedirection of the cam surface of cam 50, the lens 22being held out of contact with the cam surface by any suitable latchingmeans. Depressing shutter member 22, then, releases the latch and thelens 12 moves into the position defined by the arrested cam means 50.

OPERATION OF THE ALTERNATIVE EMBODIMENT The operation of the device issubstantially the same as previously described in connection with FIG.2. As before, the camera user depresses the range and focus determiningmember 20 to energize the motor 46 and the circuitry; the housing 44supporting the radiation source-photosensitive transducer 3l240 is thendisplaced in the direction 48. The modulated light received by the lensis passed to the photosensitive transducer 40 in the form of a centrallyhollowed cone, as indicated by the cross hatching 78, in FIG. 7. Themaximum light falls on the photocell surface d2 when the filament image36 is in true focus. At any point on either side of true focus, therefracted light pattern of the centrally hollowed cone exaggerates theout of focus condition so that substantially less light falls on thephotocell surface d2, resulting in the sharper peak depicted in FIG. 5.

Peak detection is accomplished as described in connection with theembodiment of FIG. 2, and when the true range has been determined, thecamera user depresses the shutter member 22, which first: (a) causesobjective lens 11?. to be displaced toward the stop afforded by thearrested cam 50, then (b) actuates the shutter S, and finally (0) opensswitch 53 to deenergize the motor 46 and the circuitry. The motor underthe discipline of the spring means Ell returns to the rest position, asdoes the housing 44.

As viewed in the direction indicated by the arrow $2 (FIGS. 2 and 4) onthe frontal plane orthographic projection the height dimensions of thewire filament 36 and the photoernissive surface of the photosensitivetransducer means are defined as I11 and h2 respectively. (The diameterdimension of the wire filament 36 is equal to h l.) The lenses 2i and 36have focal lengths fl and f2 respectively. The focal lengths fl and f2and the heights hi and I12 are in inverse proportion. Statedmathematically:

fl/f2=h2/fl It should be noted that the above equation holds true forequal focus lengths fl and f2 since this produces a ratio equal tounity.

The invention has been described in detail with particular reference tothe illustrated embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

ll. A camera having an electrical power supply, a light ad mittingshutter, and apparatus for determining the distance to a subject ofinterest, comprising:

a. a first lens;

I). a second lens;

c. means for emitting modulated radiant energy of predeterminedfrequency through said first lens toward the subject;

d. light sensitive means for receiving through said second lensmodulated energy reflected from the subject;

e. means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

f. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum;

g. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans;

h. first means for connecting the electrical power supply to saiddisplacing means and said electronic detection means; and

i. second means for sequentially operating the light admitting shutterand disconnecting the electrical power supply from said displacing meansand said electronic detection means. 7

2. A camera having an electrical power supply, a light admittingshutter, an objective lens, and apparatus for determining the distanceto a subject of interest, comprising:

a. a first lens;

b. a second lens;

c. means for emitting modulated radiant energy of predeterminedfrequency through said first lens towards the subject;

(1. light sensitive means for receiving through said second lensmodulated radiant energy reflected from the subject;

e. means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level;

g. utilization means for utilizing said output signal to arrest mittingshutter, and apparatus for determining the distance to a subject ofinterest, comprising:

a. a first lends having a first focal length;

b. a second lens having a second focal length;

c. means comprising a radiation surface having an effective height hl infrontal plane orthographic orientation for emitting modulated radiantenergy through said first lens toward the subject;

d. light sensitive means comprising a light sensitive surface having aheight h2 in said frontal plane orthographic orientation, said heightsI11 and h2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lens,modulated radiant energy reflected from the subject;

e. means adapted to be energized by the electrical power supply fordisplacing the said energy emitting means and said light sensitive meansin unison to vary the modulated radiant energy reflected from thesubject;

f. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level;

g. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans at a locus indicative of said maximum level of received energy;

h. first means for connecting the electrical power supply to saiddisplacing means and said electronic detection means; and

i. second means for sequentially operating the light admitting shutterand disconnecting the electrical power supply from said displacing meansand said electronic detection means.

4. A camera having an electrical power supply, a light ada. a first lenshaving a first focal length;

b. a second lens having a second focal length;

c. means comprising a radiation surface having an effective height hl infrontal plane orthographic orientation for emitting modulated radiantenergy through said first lens towards the subject;

d. light sensitive means comprising a light sensitive surface having aheight h2 in said frontal plane orthographic orientation, said heightshl and k2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lensmodulated radiant energy reflected from the subject;

e. means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

f. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level;

g. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans at a locus indicative of said maximum level of received energy;

h. first means for connecting the electrical power supply to saiddisplacing means and said electronic detection means; and

i. second means for sequentially moving the objective lens toward afocus position that is a function of said locus, operating the lightadmitting shutter, and disconnecting the electrical power supply fromsaid displacing means and said electronic detection means.

5. A camera having an electrical power supply, a light admittingshutter, and apparatus for determining the distance to a subject ofinterest, comprising:

a. a first lens;

b. first means for masking said first lens to provide a collimatedtransmission path;

c. a second lens;

d. second means for masking said second lens to provide predeterminedingress;

e. means for emitting modulated radiant energy of predeterminedfrequency through said first lens toward the subject;

f. light sensitive means for receiving through said second lensmodulated radiant energy reflected from the subject;

g. means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

h. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output sign; when the modulated radiant energy received by said lightsensitive means is at a maximum level;

. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans at a locus indicative of said maximum level of received energy;

. first means for connecting the electrical power supply to saiddisplacing means and said electronic detection means; and

k. second means for sequentially operating the light admitting shutterand disconnecting the electrical power supply from said displacing meansand said electronic detection means.

6. A camera having an electrical power supply, a light ada. a firstlens;

. first means for masking said first lens to provide a collimatedtransmission path; a second lens;

. second means for masking said second lens to provide a predeterminedingress;

. means for emitting modulated radiant energy of predeterradiant energyreflected from the subject;

electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level;

. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans at a locus indicative of said maximum level of received energy;

. first means for connecting the electrical power supply to saiddisplacing means and said electrical detection means; and

. second means for sequentially moving the objective lens toward a focusposition that is a function of said locus, operating the light admittingshutter; and disconnecting the electrical power supply from saiddisplacing means and said electronic detection means.

A camera having an electrical power supply, a light admitting shutter,and apparatus for determining the distance to a subject ofinterest,comprising:

a first lens having a first focal length; first means for masking saidfirst lens to provide a collimated transmission path;

c. a second lens having a second focal length; d.

second means for masking said second lens to provide a predeterminedingress;

means comprising a radiation surface having an effective height hl infrontal plane orthographic orientation for emitting modulated radiantenergy through said first lens toward the subject;

. light sensitive means comprising a light sensitive surface having aheight 112 in said frontal plane orthographic orientation, said heightsI11 and h2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lensmodulated radiant energy reflected from the subject;

means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

. electronic detection means, coupled to said light sensitive j. firstmeans for connecting the electrical power supply to said displacingmeans and said electronic detection means; and

k. second means for sequentially operating the light admitting shutterand disconnecting the electrical power supply from said displacing meansand said electronic detection means.

8. A camera having an electrical power supply, a light admittingshutter, an objective lens, and apparatus for determining the distanceto a subject of interest, comprising:

a. a first lens having a first focal length; b. first means for maskingsaid first lens to provide a collimated transmission path;

c. a second lens havinga second focal length;

dfsecond means for masking said second lens to provide predeterminedingress;

e. means comprising a radiation surface having an effective height hl infrontal plane orthographic orientation for emitting modulated radiantenergy through said first lens toward the subject;

f. light sensitive means comprising a light sensitive surface having aheight I12 in said frontal plane orthographic orientation, said heightshl and k2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lensmodulated radiant energy reflected from the subject;

g. means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;

h. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level;

. utilization means for utilizing said output signal to arrestdisplacement of said energy emitting means and said light sensitivemeans at a locus indicative of said maximum level of received energy;

j. first means for connecting the electrical power supply to saiddisplacing means and said electronic detection means; and

k. second means for sequentially moving the objective lens toward afocus position that is a function of said locus, operating the lightadmitting shutter, and disconnecting the electrical power supply fromsaid displacing means and said electronic detection means.

1. A camera having an electrical power supply, a light admittingshutter, and apparatus for determining the distance to a subject ofinterest, comprising: a. a first lens; b. a second lens; c. means foremitting modulated radiant energy of predetermined frequency throughsaid first lens toward the subject; d. light sensitive means forreceiving through said second lens modulated energy reflected from thesubject; e. means adapted to be energized by the electrical power supplyfor displacing said energy emitting means and said light sensitive meansin unison to vary the modulated radiant energy reflected from thesubject; f. electronic detection means, coupled to said light sensitivemeans and adapted to be energized by the electrical power supply, fordeveloping an output signal when the modulated radiant energy receivedby said light sensitive means is at a maximum; g. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means; h. first means forconnecting the electrical power supply to said displacing means and saidelectronic detection means; and i. second means for sequentiallyoperating the light admitting shutter and disconnecting the electricalpower supply from said displacing means and said electronic detectionmeans.
 2. A camera having an electrical power supply, a light admittingshutter, an objective lens, and apparatus for determining the distanceto a subject of interest, comprising: a. a first lens; b. a second lens;c. means for emitting modulated radiant energy of predeterminedfrequency through said first lens towards the subject; d. lightsensitive means for receiving through said second lens modulated radiantenergy reflected from the subject; e. means adapted to be energized bythe electrical power supply for displacing said energy emitting meansand said light sensitive means in unison to vary the modulated radiantenergy reflected from the subject; f. electronic detection means,coupled to said light sensitive means and adapted to be energized by theelectrical power supply, for developing an output signal when themodulated radiant energy received by said light sensitive means is at amaximum level; g. utilization means for utilizing said output signal toarrest displacement of said energy emitting means and said lightsensitive means at a locus indicative of said maximum level of receivedenergy; h. first means for connecting the electrical power supply tosaid displacing means and said electronic detection means; and i. secondmeans for sequentially moving the objective lens toward a focus positionthat is a function of said locus, operating the light admitting shutter,and disconnecting the electrical power supply from said displacementmeans and said electronic detection means.
 3. A camera having anelectrical power supply, a light admitting shutter, and apparatus fordetermining the distance to a subject of interest, comprising: a. afirst lends having a first focal length; b. a second lens having asecond focal length; c. means comprising a radiation surface having aneffective height h1 in frontal plane orthographic orientation foremitting modulated radiant energy through said first lens toward thesubject; d. light sensitive means comprising a light sensitive surfacehaving a height h2 in said frontal plane orthographic orientation, saidheights h1 and h2 being in inverse proportion to said first and secondfocal lengths, said light sensitive means receiving through said secondlens, modulated radiant energy reflected from the subject; e. meansadapted to be energized by the electrical power supply for displacingthe said energy emitting means and said light sensitive means in unisonto vaRy the modulated radiant energy reflected from the subject; f.electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level; g. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means at a locus indicative ofsaid maximum level of received energy; h. first means for connecting theelectrical power supply to said displacing means and said electronicdetection means; and i. second means for sequentially operating thelight admitting shutter and disconnecting the electrical power supplyfrom said displacing means and said electronic detection means.
 4. Acamera having an electrical power supply, a light admitting shutter, anobjective lens, and apparatus for determining the distance to a subjectof interest, comprising; a. a first lens having a first focal length; b.a second lens having a second focal length; c. means comprising aradiation surface having an effective height h1 in frontal planeorthographic orientation for emitting modulated radiant energy throughsaid first lens towards the subject; d. light sensitive means comprisinga light sensitive surface having a height h2 in said frontal planeorthographic orientation, said heights h1 and h2 being in inverseproportion to said first and second focal lengths, said light sensitivemeans receiving through said second lens modulated radiant energyreflected from the subject; e. means adapted to be energized by theelectrical power supply for displacing said energy emitting means andsaid light sensitive means in unison to vary the modulated radiantenergy reflected from the subject; f. electronic detection means,coupled to said light sensitive means and adapted to be energized by theelectrical power supply, for developing an output signal when themodulated radiant energy received by said light sensitive means is at amaximum level; g. utilization means for utilizing said output signal toarrest displacement of said energy emitting means and said lightsensitive means at a locus indicative of said maximum level of receivedenergy; h. first means for connecting the electrical power supply tosaid displacing means and said electronic detection means; and i. secondmeans for sequentially moving the objective lens toward a focus positionthat is a function of said locus, operating the light admitting shutter,and disconnecting the electrical power supply from said displacing meansand said electronic detection means.
 5. A camera having an electricalpower supply, a light admitting shutter, and apparatus for determiningthe distance to a subject of interest, comprising: a. a first lens; b.first means for masking said first lens to provide a collimatedtransmission path; c. a second lens; d. second means for masking saidsecond lens to provide predetermined ingress; e. means for emittingmodulated radiant energy of predetermined frequency through said firstlens toward the subject; f. light sensitive means for receiving throughsaid second lens modulated radiant energy reflected from the subject; g.means adapted to be energized by the electrical power supply fordisplacing said energy emitting means and said light sensitive means inunison to vary the modulated radiant energy reflected from the subject;h. electronic detection means, coupled to said light sensitive means andadapted to be energized by the electrical power supply, for developingan output signal when the modulated radiant energy received by saidlight sensitive means is at a maximum level; i. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means at a locus indicative ofsaid maximum level of received energy; j. first means for connecting theelectrical power supply to said displacing means and said electronicdetection means; and k. second means for sequentially operating thelight admitting shutter and disconnecting the electrical power supplyfrom said displacing means and said electronic detection means.
 6. Acamera having an electrical power supply, a light admitting shutter, anobjective lens, and apparatus for determining the distance to a subjectof interest, comprising: a. a first lens; b. first means for maskingsaid first lens to provide a collimated transmission path; c. a secondlens; d. second means for masking said second lens to provide apredetermined ingress; e. means for emitting modulated radiant energy ofpredetermined frequency through said first lens toward the subject; f.light sensitive means for receiving through said second lens modulatedradiant energy reflected from the subject; g. means adapted to beenergized by the electrical power supply for displacing said energyemitting means and said light sensitive means in unison to vary themodulated radiant energy reflected from the subject; h. electronicdetection means, coupled to said light sensitive means and adapted to beenergized by the electrical power supply, for developing an outputsignal when the modulated radiant energy received by said lightsensitive means is at a maximum level; i. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means at a locus indicative ofsaid maximum level of received energy; j. first means for connecting theelectrical power supply to said displacing means and said electricaldetection means; and k. second means for sequentially moving theobjective lens toward a focus position that is a function of said locus,operating the light admitting shutter; and disconnecting the electricalpower supply from said displacing means and said electronic detectionmeans.
 7. A camera having an electrical power supply, a light admittingshutter, and apparatus for determining the distance to a subject ofinterest, comprising: a. a first lens having a first focal length; b.first means for masking said first lens to provide a collimatedtransmission path; c. a second lens having a second focal length; d.second means for masking said second lens to provide a predeterminedingress; e. means comprising a radiation surface having an effectiveheight h1 in frontal plane orthographic orientation for emittingmodulated radiant energy through said first lens toward the subject; f.light sensitive means comprising a light sensitive surface having aheight h2 in said frontal plane orthographic orientation, said heightsh1 and h2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lensmodulated radiant energy reflected from the subject; g. means adapted tobe energized by the electrical power supply for displacing said energyemitting means and said light sensitive means in unison to vary themodulated radiant energy reflected from the subject; h. electronicdetection means, coupled to said light sensitive means and adapted to beenergized by the electrical power supply, for developing an outputsignal when the modulated radiant energy received by said lightsensitive means is at a maximum level; i. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means at a locus indicative ofsaid maximum level of received energy; j. first means for connecting theelectrical power supply to said displacing means and said electronicdetection means; and k. second means for sequentially operating thelight admitting shutter and disconnecting the electrical power supplyfrom said displacing means and said electronic detection means.
 8. Acamera having an electrical power supply, a light admitting shutter, anobjective lens, and apparatus for determining the distance to a subjectof interest, comprising: a. a first lens having a first focal length; b.first means for masking said first lens to provide a collimatedtransmission path; c. a second lens having a second focal length; d.second means for masking said second lens to provide predeterminedingress; e. means comprising a radiation surface having an effectiveheight h1 in frontal plane orthographic orientation for emittingmodulated radiant energy through said first lens toward the subject; f.light sensitive means comprising a light sensitive surface having aheight h2 in said frontal plane orthographic orientation, said heightsh1 and h2 being in inverse proportion to said first and second focallengths, said light sensitive means receiving through said second lensmodulated radiant energy reflected from the subject; g. means adapted tobe energized by the electrical power supply for displacing said energyemitting means and said light sensitive means in unison to vary themodulated radiant energy reflected from the subject; h. electronicdetection means, coupled to said light sensitive means and adapted to beenergized by the electrical power supply, for developing an outputsignal when the modulated radiant energy received by said lightsensitive means is at a maximum level; i. utilization means forutilizing said output signal to arrest displacement of said energyemitting means and said light sensitive means at a locus indicative ofsaid maximum level of received energy; j. first means for connecting theelectrical power supply to said displacing means and said electronicdetection means; and k. second means for sequentially moving theobjective lens toward a focus position that is a function of said locus,operating the light admitting shutter, and disconnecting the electricalpower supply from said displacing means and said electronic detectionmeans.